scripts/pythondistdeps: Fix for Python 3.10

self.name in PathDistribution is a property in Python 3.10+ and thus we
can't redefine it as an instance variable. Instead we explicitly define
it as a property, which works on all supported Python versions.

pythondistdeps.py

@@ -53,7 +53,6 @@ class Requirement(Requirement_):
 class Distribution(PathDistribution):
     def __init__(self, path):
         super(Distribution, self).__init__(Path(path))
-        self.name = self.metadata['Name']
         self.normalized_name = normalize_name(self.name)
         self.legacy_normalized_name = legacy_normalize_name(self.name)
         self.requirements = [Requirement(r) for r in self.requires or []]
@@ -61,6 +60,11 @@ class Distribution(PathDistribution):
             v for k, v in self.metadata.items() if k == 'Provides-Extra']
         self.py_version = self._parse_py_version(path)
 
+    @property
+    def name(self):
+        """Return the 'Name' metadata for the distribution package."""
+        return self.metadata['Name']
+
     def _parse_py_version(self, path):
         # Try to parse the Python version from the path the metadata
         # resides at (e.g. /usr/lib/pythonX.Y/site-packages/...)